Authorities said there were five people at the home at the time of the incident -- two adults and three children, including the two victims.

A neighbor said she heard screaming.

"It sounded like something was wrong," said Donelle Kennedy, who lives nearby.

Kennedy said she heard cries for help Thursday morning at a home on Valencia Avenue in Holly Hill.

"I don't know why they're allowed to get out of someone's sight for that long for that to happen," Kennedy said.

A crime scene unit and investigators spent all day at the home looking for answers to these questions.

Investigators said it appears the toddlers got past two adults and a 5-year-old before finding their own way to the backyard pool. The two victims were related, but the 1-year-old was just visiting, according to investigators.

"We'll look into everything we can and figure out what happened," Gant said.

Investigators said the mother to one of the victims was taken away in a deputy's cruiser for questioning, while the second adult in the house was medically treated for shortness of breath.

It's still too early to tell if charges will be filed.

"I could not imagine. I could not imagine," Kennedy said.

The Florida Department of Children and Families is investigating this incident. Authorities said the 5-year-old at the home is in protective custody with DCF. Another 3-year-old child lives at the home, but wasn't there for today's incident. DCF has told the mother of that child to leave the home with that child.

This is the third child drowning death in Volusia County in two weeks. The sheriff's offices Major Case Unit is investigating.